When multiple storage systems are connected together, typically by means of a Storage Area Network (SAN), it is typical that logical relationships are created between devices. These relationships are sometimes known as mappings. These mappings provide the detailed information about a group of systems and which logical parts of the target system (typically a storage controller) can be accessed by the initiator system, typically a host or another storage system (perhaps a storage virtualization system). These relationships are typically described in terms of the specific World Wide Port Name (WWPN), or group of WWPNs of the Initiator, the WWPN, or group of ports, or all ports of the Target. The Initiator-Target relationship may be described in terms of a group of Logical Units, and for each Logical Unit, a Logical Unit Number, or LUN.
Taking a simple example, as illustrated in FIG. 1:                a. A Storage controller (102) has ports AA (108) and BB (110);        b. A Host system (100) has ports XX (112) and YY (114); and        c. The storage controller (102) has logical Units 01 (104) and 02 (106).        
A set of port relationships to allow the Host system (100) to access a group of logical units in this exemplary system might be:                a. AA to XX;        b. AA to YY;        c. BB to XX; and        d. BB to YY.        
For this host-storage group the logical unit number (LUN) assignments might be:                a. Logical Unit (LU) 01 accessed at Logical Unit Number 00        b. Logical Unit (LU) 02 accessed at logical Unit Number 01.        
Thus, in FIG. 1 there is shown in schematic form an apparatus or arrangement according to the prior art, in which host 100 is aware of host LUs 116, 118. Host 100 has ports AA and BB (respectively 108, 110), which are connected to storage controller 102 through storage controller ports YY and XX (respectively 114, 112). Storage controller 102 controls and is in communication with logical units 01 and 02 (respectively 104, 106).
Most storage systems have a similar access model, as this is largely driven by the common interfaces defined by SCSI and Fibre Channel standards.
A common problem with storage systems, particularly as they grow larger and more complex, is the increasing chance of an administrator making an incorrect change to the configuration by accident. For the example given above, it is easy to see how an administrator could confuse the logical unit ID in the storage controller with the logical unit number seen by the host system, leading to a loss of access and/or data if they then reconfigured the wrong underlying LU. Most conventional systems will provide generalized warnings that changes may cause loss of data and some provide a general warning that making a change may cause loss of access. However, these warnings are generalized and occur so commonly that they may be ignored by users for lack of specificity.
It would thus be desirable to have an improved technology for alleviating confusion and thus preventing at least some errors during the process of changing the configuration of a storage network.